The Difference Between Farther and Further

Many people use “further” and “farther” interchangeable, but, in fact, they mean slightly different things. “Farther” refers to a physical distance, while “further” refers to a figurative distance. So, when wondering how many more miles or kilometers to a particular destination, you’d say, “How much farther to the gas station?” On the other hand, when speaking of a figurative measure, you should use “further”. For instance, “Nothing could be further from the truth.”

Probably the best way to remember the distinction between “farther” and “further” is to think about where you’d use the word “furthermore”. In this case, you use it much like “in addition to”, which is tied to something figurative. So just remember “farther” = “physical” and “further” = “figurative”.

“interchangablY”… As far as I am aware, American English also uses adverbs BTW, Canadian English uses both for all contexts as well, especially in the east. The west was settled by a different kind of folk.

<Mnemonically I prefer to think as "Farther" contains the word "Far" with contains the concept of distance. "Further contains the word "fur" with has absolutely nothing to do with "Further" real meaning.